I was given a sample of pond water
to examine and report on the content.

Having viewed several 'drops' of
the sample, only Tracehelomonas and Euglena appeared to be
present.

However having viewed for a while,
using the high power, I noticed an out of focus movement. Focusing
in I saw that this was an amoeboid form.

Viewing its movement and general
appearance, with the video microscope, I formed the opinion that it was
an amoeba of the Naegleria genus.

These are small amoebae, around 30µm
and monopodial. The pseudopodia develop in a series of eruptive bulges,
to one side of the anterior margin of the cell.

Visible in the accompanying image
are the hyaline cap, and the contractile and food vacuoles. Also,
posteriorly, can be seen the temporary uroid.

Brightfield, 40x objective.

Naegleria is interesting in
that one of the species, N. fowleri, is a lethal pathogen in man
causing primary amoebic meningo-encephalitis. This enters the central nervous
system via the nasal passages. Also interesting is that it grows at temperatures
of around 30ºC, though is quite happy at temperatures in the mid 20ºC
region. The latter being the temperature of heated swimming pools.

Although N. fowleri is considered
to be the lethal pathogen, N. gruberi is not yet entirely in the
clear.

Species identification is very much
a specialist procedure and cannot be achieved by light microscopy alone.

In view of the nature of some
organisms which may be found in pond water, it is advisable, especially
for anyone attempting to isolate and grow protozoa, that at least basic
standards of cleanliness and safe practice should be adopted.

Practices such as mouth pipetting
and eating or drinking in the culture area should be strictly taboo.

There should also be facilities
for cleaning, by disinfectants, or disposal of contaminated glassware and
discarded cultures.